Liquid color is metered from containers. When the liquid runs out and a process machine, namely an injection molding machine or extruder, is operating producing plastic parts, there is a time period where no color is being metered, and production parts must be scrapped because they do not get the required color. One solution is to alarm when color level is low, and change the liquid color container before the liquid color runs out. However, this results in the remaining liquid color being wasted, or a mess due to spillage, when transferring the remaining liquid color into the new container.
A better solution is to simply refill the container before the liquid color runs out. Currently available systems for doing this involve a level sensor to detect low level in the primary container, and then a reserve container and pump standing by for refilling the primary container.
The reserve container may be small, but preferably is large enough to last for many weeks. Two thousand pound capacity totes are standard in the industry.
This reserve container may be very close, or may be located at some distance. In either case a pump is required for the reserve container for transferring the liquid color into the primary container.
Factories always have many process machines. Each requires its own primary supply of color, and its own metering pump. In current systems if, for example, 5 process machines are running and automatic refill of these containers is desired, then each process machine requires its own “reserve” container and a reserve pump as well. This need for 5 reserve containers and 5 pumps is still present even if all process machines are running the same color.